Hydraulic pit prop



Feb. 11, W69 F. s. ALLlNQUANT 3,426,995

HYDRAULIC PIT PROP Sheet Filed Dec. 19, 1966 Feb. 11, 1969 v F. s. ALLINQUANT 3,426,995

HYDRAULIC PIT PROP Filed Dec. 19, 1966 Feb. 11, 1969 F, s, ALUN UANT 3,426,995

HYDRAULI C PIT PROP Sheet Feb. 11, 1959 F. s. ALLINQUANT 3,426,995

HYDRAULIC PIT PROP Filed Dec. 19, 1966 Sheet Q 0: 4

United States Patent 9 Claims ABSTRACT OF THE DISCLOSURE The invention mainly relates to a support of a hydraulic pit prop having the conventional filler, release, and slide valves wherein the support has a cylindrical recess which accommodates the release valve housing and two cylindrical bores which respectively accommodate the slide valve housing and the filler valve housing, and wherein said recesses are at right angles to the cylindrical recess, the release valve housing itself having two bores, the housings of the filler and of the slide valves running through the two bores of the support and each penetrating into respective ones of the two bores of the release valve housing, the whole assembly being made fast by a U-shaped clip.

This invention relates to a hydraulic pit prop or like hydraulic jack device.

A hydraulic pit prop is basically a hydraulic jack which serves to provide support at the working face of a mine gallery. Such a pit prop is pressurised by means of a gun device which transfers hydraulic fluid under pressure, this imparting a lifting force which is referred to as the installation load. The end of the said gun device is engaged in the socket of the pit prop afforded by a filler element equipped with a check valve.

After pressurisation, the pit prop must subsequently yield slowly under the effect of earth pressure by discharge of the hydraulic fluid through a valve which is termed the slide valve. This is a calibrated valve which allows the hydraulic fluid to escape when a predetermined pressure is exceeded; the quantities of fluid passing through this valve are extremely small and the movements involved are correspondingly extremely slow.

Release of the pit prop, which is called collapsing, is effected by rapidly discharging it through a valve known as the collapsing valve. This valve should present a large flow cross-section and be capable of operation with the minimum of input effort, in order, when necessary, that it can be remote-controlled to avoid any danger to personnel by a roof fall. It is also necessary that the collapse of the prop should take place as rapidly as possible under its own weight.

The complete pit prop assembly is subjected to extremely severe operating conditions, in a dusty atmosphere, and is exposed to violent impact loading during installation and at the time of collapse. For this reason, all the vulnerable elements, such as the valves, must be protected, but nevertheless should be easily accessible in order to enable them to be replaced, if necessary, at the bottom of the mine shaft, without the need for any special tools or equipment.

The object of the invention is to provide a number of improvements which will permit production of a pit prop satisfying these requirements, and which furthermore enable other advantages such as simplified manufacture and simple operation to be obtained.

The invention, therefore, is directed to a support of a hydraulic pit prop or analogous hydraulic jack de- 3,426,995 Patented F eb. 11, 1969 vices comprising filler, release or collapsing, and slide valves, the invention requiring that the collapsing valve and the slide valve, and preferably also the filler element, are constituted by separate elements which, while being fitted in a sealed manner, are locked in seatings in a hollow mounting rigid with the cylinder of the pit prop and communicating with the compression chamber of the latter, in order that said cylinder and said mounting eflectively form a common block.

In one embodiment, a first element, preferably that comprising the collapsing valve, is slidably engaged in its seating and contains, disposed transversely to the axis thereof, recesses in which other elements locate when slidably inserted into their own respective seatings, where they are locked by a simple key arrangement.

Advantageously, a decompression device will be provided which operates when the piston of the pit prop is at its full extension, this in order that the pressure in the pit prop is collapsed once the pit prop has reached maximum extension. In accordance with a further feature of the invention, the decompression function is effected by the collapsing valve itself. To this end, the valve block, which is preferably fixedly attached to the upper part of the cylinder, is advantageously arranged in such a fashion that the collapsing valve is actuated by the piston at the end of its travel.

In accordance with another further feature of the invention, the cylinder of the pit prop is constituted by a cylindrical tube fixed at both of its ends in a nonwelded manner. Thus, this tube may be attached to the base by a keeper ring and the mounting for the valve block may be fixed to the tube by a ring and bolt arrangement. This design has the advantage that it is possible to use a drawn tube which contains no irregularities and does not require any internal machining after assembly, something which is necessary when a welded assembly is employed.

The following description, relating to the accompanying drawings, is given by way of a non-limitative example and will indicate how the invention may be carried into effect.

In the drawings:

FIGURE 1 illustrates a hydraulic pit prop seen in vertical section;

FIGURE 2 is an elevational view of the upper part of the pit prop;

FIGU'R ES 3 and 4 are horizontal sections, taken respectively on the lines -IIIIII and IV-IV, of FIG- URE 1;

FIGURE 5 is a horizontal section on the line VV, of FIGURES 1 and 2;

FIGURE 6 is a perspective view of the pit prop, on a smaller scale, with an exploded view of the valve block elements.

The hydraulic pit prop illustrated is of the piston and cylinder type, as opposed to the telescoping tube type. The cylinder 1 is constituted by a cylindrical tube attached at its lower end, through the medium of a keeper ring 2, to a ring 3 which is itself screwed by means of screws 4 to a flange 5a on a socket 5 forming the base of the cylinder. As FIGURE 1 shows, this socket 5 is constituted by a disc 5b forming the cylinder base, on which there are formed an upward-projecting cylindrical flange constituting the flange 5a and a downward-projecting skirt 50 which spigots into a socket 6 forming the base of the pit prop, where such skirt is attached at 611. Sealing at the base of the cylinder is provided by an annular seal 7 located in a grove 7a in the external face of the tube 1 and trapped between the latter and the internal face of the flange 5a, and by a sealing ring 8 locked by the screws 4 between the upper face of the flange 5a and the lower face of the ring 3. This assembly enables a very robust pit prop base to be produced, which can take a variety of forms and be made of a variety of different materials and is readily fitted to the base of the cylinder. The described manner of assembly provides advantages as compared with conventional processes which employ welding, these processes being complicated from the point of view of sealing and from the point of view of the risk of distortion in the components.

The piston, which is generally designated by the reference 9, is equipped in known fashion with a seal and a friction ring 11, these being fixed in place by an associated component 12. This piston itself does not constitute part of the invention and detailed description thereof is unnecessary. The piston rod 13 is constituted by a tube attached at its bottom end to the piston 9 and at its top end to a head portion 14; this assembly is not sealed and can be produced in any desired manner, for example by a force-fit arrangement, complemented by a keeper ring such as 13a or by suitable screw means. The upper part of the cylinder tube 1 comprises a friction ring 15 in which the rod 13 can slide. The piston and its rod are therefore guided for sliding motion by the ring 11 rigid with the piston and by the ring 15 rigid with the cylinder. These rings will advantageously be made of sintered bronze impregnated with polytetrafiuoroethylene, a material commerically available under the trademark DU.

The pressurizing of the pit prop is effected through the medium of a tube 16 which extends down the outside of the cylinder and is force-fitted, at its bottom end, into a bore 17 in the base portion 5, where a seal 16a is provided. The bore 17 communicates with an undercut 17a in the flange 512, into which opens an annular throat 18 in said flange. Holes 19, formed in the tube 1 opposite the said throat, allow the tube 16 to communicate with the interior of the cylinder. FIGURE 1 illustrates the pit prop in the fully retracted state. The friction ring 11 of the piston in this condition partially covers the holes 19, however the clearance formed in the bottom part of the piston 9 are sufiicient to enable the pressurised fluid arriving through the tube 16 to penetrate beneath the piston and lift it; the holes 19 are then completely open for passage of fluid.

The tube 16 is spigoted at its top end, where a seal 16b is provided, into a bore 20a in a hollow mounting 20 forming a valve block. This mounting 20, which can be seen in FIGURES l, 2, 5 and 6, comprises a portion 20b in the 'form of a sleeve, having a projection on one side in the form of a boss portion 200 which constitutes the specific part for receiving the valves. The sleeve 20b is slidably engaged over the tube 1, is supported by a keeper ring 21 located in an external throat in said tube, and is locked against upward movement and against rotation by two screws 22 which screw into the sleeve and have unthreaded tip portions 22a which penetrate into holes 22b in the tube.

The base of the vertical bore 20a communicates through a horizontal passage 23 with the bottom part 24:: of a vertical bore 24. The entry portion of this bore 24 is counterbored at 24b to give a larger diameter, and opens into the horizontal face 251: of a milled parallelepiped recess 25 which, together with the portion 200, defines two vertical lugs 26 and 27. These lugs are respectively traversed (FIGURES 5 and 6) by horizontal bores or drillings 28 and 29 counterbored at their entry portions, 280 and 29a. The bores or drillings 28 and 29 may hereafter he termed first bore and third bore, respectively. The vertical face 25b forming the base of the milled recess 25 is pierced by a bore 30 in which there can slide (FIGURE 1) a finger 31 which passes through a hole 31a in the tube 1 when the mounting 20 is in place, so as to be engageable with the rod 13 of the piston 9.

In order to drill the passage 23, it is necessary for it to open externally at 2311. The opening 23a should normally be closed off; this can be done by using a screwed plug but such opening will in fact preferably be used to con nect a manometer type pressure gauge, as will be described hereinafter.

The element containing the collapsing valve is constituted by a parallelepiped block 3 which is assembled in the milled recess 25. This block 32 has projecting from its bottom face 32 a cylindrical sleeve 32b which engages in the enlarged entry portion 24b of the bore 24, where a seal 33 is provided, whilst its vertical face 32c abuts the vertical face 25b forming the base of the milled recess. The internal bore of the sleeve 32b, which opens at the bottom end into the section 24a of the bore 24, opens at the top end into a cavity 34 which contains the collapsing valve, as will be described hereinafter. Into this cavity 34, there open laterally bores 35 and 36 which, when the block 32 is assembled in place, open coaxially into the bores 28 and 29 respectively. Bore 35 may hereafter be referred to as second bore. The bores 35 and 36 have the same diameter at their input portions as the bores 28, 29 and open into the cavity 34 through smaller diameter portions 35a, 36a.

The slide valve and the filler device are respectively contained in two elements or housing 37, 38, each having the external form of a cylinder 37a, 38a provided with a larger diameter head 37b, 38b and a tail portion of smaller diameter 370, 38c. These elements 37 and 38 locate respectively in the mating bores 28, 35 and 29, 36, sealing being ensured by seals 39, 39a located respectively between the tail portions 370, 38c and the Wall portions of smaller diameter, 350, 36a of the bores 35, 36. A U-shaped clip 40, having arms which form two tongues 40a, 40b recessed respectively at 40c, 40d, locks the assembly in place, embracing the block 32 in such a manner that the said tongues are inserted between the lateral faces of the block 32 and the milled recess 25, the recesses 40c and 40d of the said tongues locating in annular grooves 37d and 38d of the cylindrical portions 37a, 38a of the elements 37, 38, as indicated in FIGURE 5. The valve assembly thus being in place, and the cavity 34 communicating via the tube 16 with the interior of the pit prop cylinder and being thus subjected to the same pressure as prevails therein, this pressure tends to force the block 32 upwards and thus to force the elements 37 and 38 towards the left and right respectively. The upward thrust exerted on the block 32 is resisted through the large-area surfaces of the elements 37 and 38 by the walls of the bores 28, 29 in the mounting 20 on the one hand, and by those of the bores 35, 36 in the block 32 on the other; the forces exerted on the elements 37 and 38 are resisted by the tongues 40a and 40b which act as keys in shear. The clip 40 therefore carries no vertical load. It is simply held by a captive nut 41 in its base 402, which screws on to a threaded pin 41a in the block 32. To dismantle the valves, when the pit prop is not under pressure, all that is necessary is to release the nut 41 and withdraw the clip, the elements 37 and 38, then the block 32.

The valves themselves are illustrated in FIGURES 1 to 5. The collapsing valve 42 is lodged in the internal cavity 34 of the block 32. It is of the differential type, that is to say it comprises a valve head 42a co-operating with a valve seat 43, this head being extended by a tail portion 42b the diameter of which is very near to the effective seat diameter, such that the pressure in the cavity 34 applies the head 42a of the valve against its seat with a moderate force only. A spring 44 supplements this seating force and keeps the valve closed when the pit prop is not under pressure. The tail 42b of the valve projects outside the cavity 34 through a bore 34a in which an O-ring 34b is arranged, and terminates in a ring 45 which can slide in a milled slot 46 formed at the rear of the block 32 and traversed by a drilling 460. When the valve is closed, the ring or eye 45 is slightly staggered in an inward direction in relation to the drilling 46a and the collapsing valve is in fact opened by the introduction of a key 47 (FIGURE 6), the end of which has an elliptical section. When this key is turned, its tip 47a having been inserted into the bore 46, the valve assembly is withdrawn towards the exterior. Due to the small difference in crosssection between the effective section of the valve head 42a and its tail portion 42b, the force which has to be exerted for this withdrawal movement is virtually independent of the pressure in the pit prop and the flow cross-section of the valve can be very large, which is essential in the context of the collapsing function. When the valve is opened, liquid flows from the cavity 34 past the seat 43 into the space 48 which communicates freely with the exterior, through orifices which are not shown.

The collapsing valve extends beyond its head 42a in the form of a rod 420 in contact with the finger 31. The piston 9 is provided at its top end, outside the rod 13, with an inclined ramp 49 which, when the piston is at the end of its travel (full extension of the pit prop), strikes the finger 31 and forces it towards the left, lifting the valve 42. The latter is thus opened and end-of-travel decompression is achieved.

The slide valve 50 is located inside the element 37 (FIGURE This valve is a simple discharge valve which can take a number of forms. In the drawing, a valve of the ball type, loaded by Belleville type washers 50b, has been illustrated.

The ball 50a normally closes off a discharge passage 51 in the element 37, such passage opening into the cavity 34. When the pressure in this cavity exceeds a preset limit, the ball 50a is lifted against the load of the Belleville type washers 50b and the liquid escapes through the passage 51 past the said ball, then to the exterior through the clearances in the valve or through orifices provided for the purpose.

The filler device is contained in the element 38. It is constituted by a sleeve 52 looked in place by the screwed head 38b, a seal 53 being interposed, said sleeve being arranged in a bore 54 in the element 38 communicating through a passage 54a with the cavity 34. This sleeve 52 contains a blind axial hole 52a communicating through a plurality of radial holes 52b with an annular throat 520 which itself communicates through passages 52d with the base of the bore 54 and the passage 50a. A lip seal 55 is trapped between the seal 53' and the face of the peripheral annular wall of the portion 38a of the element 38, and acts as a non-return valve. The design and operation of the bore 52a, which is intended to receive the end of a filler gun, and the design and operation of the radial holes 52b, do not form part of the present invention and have been described in detail in the specification of the present applicants concurrent French patent application No. 43,417/ 65. 'It need merely be stated here that the end of the gun device is automatically locked in the bore 52a under the pressure of the hydraulic fluid delivered by said gun. The fluid passes through the holes 52b, lifting the lip seal 55, into the throat 52c and thence through the passage 54a into the cavity 34 which communicates through the tube 16 with the interior of the pit prop cylinder. When the latter is under pressure, the gun is withdrawn and the non-woven valve constituted by the lip seal 55 prevents the fluid from escaping through the holes 52b.

It is desirable, in order to be able to check that the pit prop is operating satisfactorily, to provide a pressure gauge connection which can be used without making communication with the interior of the cylinder and creating an additional volume which could cause an appreciable drop in the operating pressure. For this purpose, the bore 23a (FIGURE 1), created in order to drill out the passage 23 in the mounting 20 and which has normally to be closed off in some fashion or other, is used for the pressure gauge connection. In the embodiment illustrated, the bore 23a is provided with a screw thread 56 at its entry end, into which a threaded sleeve 57 is screwed in which there can slide a perforated rod 58 the external tip 58a of which carries a screw thread or some other device to which a pressure gauge can be attached. This screwed rod 58 has a tip 58b which bears against the end of the sleeve 57 and can slide inside a sleeve 59a forming the external end of a valve body 59 the internal end of which abuts a shoulder in the bore 23a. This body 59 contains a valve 60 the head of which is kept in contact with its seat on the one hand by a spring 61 and on the other hand by the pressure prevailing in the cavity 34 whilst the pit prop is in service. The spring 61 is seated at the left on a perforated plate 60a integral with the rod 60, which plate is in contact with the head or tip 58b. In order to use the gauge, the sleeve 57 is screwed into the thread 56, causing the tip 58b to slide inwards and push the plate 60a to the right, opening the valve 60.

If it is not desired to use the gauge, the assembly can be withdrawn and replaced by a threaded plug screwed into the thread 56.

Since it is necessary to fix the mounting 20 against rotation, using the tipped screws 22, in order to ensure correct positioning of the finger 31 in relation to the tube 1 and correct positioning of the bore 20a in relation to the tube 16, it is impossible for said mounting 20 to be rotatable on the cylinder 1. However, it is well known that in mines, installed pit props are often used as a strong point for winching, and the forces developed in this context can amount to as much as 4 metric tons. With this in mind, to afford a strong point there is provided a handle 62 attached to a ring 62a, the latter being rotatably mounted in a throat 63 created at the bottom end of the portion 22b of the mounting 20. This arrangement prevents oblique tensile forces from being exerted upon the cylinder of the pit prop. In contrast, if the handle were fixedly arranged on the mounting 20, the winching forces might well be exerted out of line and the cylinder thus twisted and pulled over.

The tube 16 is protected (FIGURES 1 and 4) by a profiled section 64 vertically arranged along the cylinder 1 between the ring 3 and the mounting 20 of the valve block, and the cylinder will advantageously be protected by a casing 65 of flexible material interrupted to pass the profiled section 64 and itself enclosed by a thin sheet 66. The body of the pit prop, including the tube 16, is thus completely enclosed and protected.

Various modifications of the above-described arrangement are possible within the scope of the invention as defined by the appended claims.

What I claim is:

1. A hydraulic jack device such as a hydraulic pit prop, comprising a body designed to be supported upon the ground and including a cylinder having a base and an open extremity; a piston which is mounted in said cylinder in sliding fashion and defines in conjunction therewith, be tween itself and the cylinder base, a compression chamber; a piston rod rigid with the said piston and adapted to extend outside the said open extremity of the cylinder in order to support a load; filler means incorporating a check valve and adapted to be connected to a source of pressurized fluid in order to supply such fluid to the said compression chamber; a collapsing device incorporating a discharge valve designed to be opened by a control means in order to evacuate the said compression chamber; an overload device including an overload valve adapted to open at a predetermined over-pressure in said compression chamber; a mounting fixed to the said body and provided with a cylindrical recess and with a first cylindrical bore whose generatrices are perpendicular to the generatrices of said cylindrical recess, said recess and said first bore having in common a cavity communicating with said compression chamber; the cylindrical block, adapted to slide tightly in said cylindrical recess, of said discharge valve, said block being provided with a second bore which, when said block lies at the bottom of said cylindrical recess, faces said first bore; and the cylindrical housing of said overload valve, said housing being adapted to penetrate into said first bore and beyond said first bore into said second bore when said block lies at the bottom of said cylindrical recess.

2. The device according to claim 1, wherein said housing is provided with an annular groove which, when said housing penetrates into said second bore, lies outside said block, and a clip secured to said block penetrates into said transverse groove when said block lies at the bottom of said recess.

3. The device according to claim 2, wherein said recess has a plane of symmetry, said mounting is provided with a third cylindrical bore substantially symmetrical of said first bore with respect to said plane, said third bore contains the second cylindrical housing of a filler device, said clip is U-shaped and penetrates into the annular grooves of both said first and said second cylindrical housings.

4. The device according to claim 2, wherein said clip is provided with a screw adapted to secure said clip to said block.

5. Device as claimed in claim 1, including a tripping element arranged at the end of the working travel, and designed to be operated by the piston when at its full extension in order to open the discharge valve.

6. Device as claimed in claim 5, in which the mounting is attached near the upper end of the cylinder and the tripping element is a finger slidably projecting through an aperture in the cylinder and adapted to operate the discharge valve.

7. Device as claimed in claim 1, comprising a pipe passing outside the cylinder between the mounting, attached at the top of the cylinder, and the cylinder base, in order to form a transfer arrangement between said valved chamher and said compression chamber, and comprising a profiled section attached to the cylinder in order to protect said transfer arrangement over the full extent of its length.

8. Device as claimed in claim 1, including an annular portion on the mounting surrounding the cylinder and containing an annular throat, and a ring carrying a handle and adapted to rotate in said throat.

9. Device as claimed in claim 1, including a sleeve integral with the said mounting, a ring engaging in an annular throat in the cylinder in order to support said sleeve, a device equipped with locking screws designed to screw radially into the sleeve, and seatings formed in the exterior of the cylinder in order to receive the ends of said locking screws.

References Cited FOREIGN PATENTS 1,131,625 6/ 1962 Germany.

1,150,640 6/1963 Germany.

1,152,080 8/1963 Germany.

720,361 12/ 1954 Great Britain. 970,917 9/ 1964 Great Britain.

RAY D. FRAZIER, Primary Examiner.

FRANK DOMOTOR, Assistant Examiner.

US. Cl. X.R. 

